The field of the invention is that of supplying electrical energy, for a load of unknown value, without mechanical contact, in particular outdoors and in public places.
Electrical energy from a public or private mains supply is currently made available through a simple connection medium in the form of a socket outlet. This medium has many advantages, the main one of which is the very low acquisition cost for the user.
Nevertheless, this medium has major drawbacks, the main ones of which can be summarised as follows:
different standards in different countries often make the various kinds of male and female connector incompatible, PA1 any socket outlet supplying energy must protect its conductors by means of mechanical components, PA1 the safety of the user must be assured regardless of defects of the installation (differential circuit-breaker), and PA1 the mechanical connection is subject to all kinds of hazards (water, oxidation, poor contact, etc). PA1 a part called the base which is buried and/or embedded in a wall, comprising a first induction coil energised by an electrical mains supply. The base is energised from the mains supply with a single-phase current or preferably, because of the power transmitted, a three-phase current, generally at 50 or 60 Hz and 230 volts (depending on the country concerned); this frequency is stepped up by an electronic stage functioning as a resonant inverter which uses IGBT components to provide a current chopped at a frequency of approximately 20 kHz or more. The resulting current is delivered to the induction coil at a voltage of approximately 350 V via a cable. The induction coil is in the form of a plate approximately 22.5 cm in diameter housing six concentric turns. Each turn is the result of braiding almost 1,000 insulated wires each having a diameter of 0.18 mm. The first coil has an intermediate output, enabling transmission of only part of the power, and PA1 a mobile part, called a terminal, comprising a second induction coil supplying at least one socket outlet and designed to be placed opposite said base to enable inductive coupling between said first and second coils so that electrical energy received from said electrical mains supply can be transmitted to said socket outlet(s) with no electrical connection between said base and said terminal. The electronics of the mobile part rectify a 350 V current picked up by the receiver plate which is converted to a 230 V alternating current by a conventional inverter stage to supply approximately 4 to 6 kW of power. PA1 converting a low-frequency electrical signal received via said electrical mains supply into a high-frequency electrical signal feeding said first coil; PA1 detecting the presence of and/or identifying said terminal. The optimum efficiency of the system is conditioned by a concentric disposition of two plates placed one on the other. To obtain this result the centre of the sender and receiver plate has a 3 cm diameter hole in it. This hole contains a ring magnet which forms a force-fit ring. The intensity of the magnetic field detected when the two magnets interact with each other triggers or does not trigger, depending on the setting, the operation of the optical interface of the communication receiver described below and consequent emission of an inductive field from the coil of the buried base to the receiver coil. Another possibility is to use the intermediate output of the coil of the base; energising only this source coil part generates a low power just sufficient to establish communication with the mobile part. When the mobile part is recognised, following an exchange of information between the stud and the terminal, a mechanical contact or one with no moving parts connects the remainder of the source coil and all of the power is transmitted. PA1 validation of transfer of energy between said coils. PA1 limitation of the transmitted power. This limitation is effected by a regulation algorithm programmed in a REPROM enabling the buried electronics to react to varying calls for power from the terminal. PA1 transfer of data to a centralised device, for example by modulating a power line carrier current. This can allow centralised billing for the supply of current, for example. PA1 an indicator to indicate that energy is being transferred, PA1 at least one electrical socket outlet to a known standard, PA1 a reader for a portable memory device for authorising use of said terminal and/or paying for electrical energy consumed, PA1 dedicated electrical equipment, such as a lamp on a pole, an illuminated cone, emergency equipment, and PA1 at least one carrying handle. PA1 mechanical guide means for placing said terminal on and/or attaching it to said base, and PA1 optical means transmitting an optical signal in the visible or invisible spectrum, for example an infrared signal, from said terminal to a corresponding sensor in said base.
In other words, the socket outlet is perfectly suitable for most purposes but inevitably gives rise to problems under some conditions of use. This is the case in particular with socket outlets installed outdoors, in particular buried ones, which have to work in severe surroundings due to their environment and the climatic conditions to which they are exposed: coastal atmosphere, dust, rain, violent storms, etc., and even vandalism in the case of outlets in public places.
Communities are becoming concerned about the use of buried outlets for connecting to the EDF mains supply in public places, because of the maintenance costs that they generate. The solution that entails placing them in boxes above ground contributes to cluttering public places and thoroughfares with street furniture. Electrical power distribution cabinets and terminals for various uses (payment, security, lighting, telecommunications, etc.) are continually "sprouting". The profusion and diversity of these outdoor "boxes" and the works and costs to which they give rise are worrying local councillors.
For any community, a good electrical energy distribution system is one which is unseen, which does not clutter the environment and which is available without specialist intervention. Councillors are currently in favour of solutions which make the consumer pay the costs.
In the field of electrical energy distribution terminals, the use benefits the user, but the residents have to put up with the cluttered environment.
The erection of fixed terminals which divide marketplaces into a grid makes it difficult to convert the area for other local events. Access to energy is also highly localised, with a procedure for opening or closing all of the mains supply to the platform.
Multiple uses are encountered with multiple electrical mains supplies. Thus electric cars use their own mains supply on the public thoroughfare, municipal services their dedicated outlets. Other outlets are used for public utility services and by street sellers for their scales and heating appliances.
Another aspect is that access to the electrical mains supply, in France in particular, is not valued. For 50 years the French have been consuming electricity without concerning themselves with the mains supply that delivers it. Electricity has been "on offer", so to speak. With the same mind-set, communities are reluctant to invest in a "public" socket outlet, even a buried one. For the end user the price must be low, and the means for supplying energy are of no interest provided that energy is available.
Availability is the main quality required of buried electricity distribution terminals. This continuous operation constraint leads to high maintenance costs for buried outlets, which are exposed to all the hazards of the thoroughfare. Initial trials indicate annual costs of 70,000 to 80,000 francs per 100 terminals and that faults are often of mechanical origin or associated with the ingress of rainwater or cleaning water.
The cost can be significantly reduced with installations that have no moving parts.
Also, issuing a VAT-inclusive invoice for electricity in small amounts (17.25 francs, for example) is not universally acceptable and does nothing to simplify accounting procedures. From this point of view, self-service access would simplify the relationship between the end user and the supplier of energy through prepayment, eliminating the need for authorisation and specialist personnel for making the connection.
The technologies employed at present are essentially electromechanical for which preventive maintenance is not enough. They must resist the severe conditions of their environment. Cleaning with high-pressure water jets drives rubbish and mud into the wells and socket outlets.
A lock which sticks, a valve that fails to close, rough handling, these are all causes of faults associated with the condition of retraction of the socket outlets and access to them via a trapdoor.